use std::collections::hash_map::HashMap;
use std::path::{Path, PathBuf};
use std::str::FromStr;

use mime::Mime;
use quote::ToTokens;
use syn::punctuated::Punctuated;

use crate::config::{get_template_source, read_config_file, Config};
use crate::CompileError;
use parser::{Node, Parsed, Syntax};

pub(crate) struct TemplateInput<'a> {
    pub(crate) ast: &'a syn::DeriveInput,
    pub(crate) config: &'a Config<'a>,
    pub(crate) syntax: &'a Syntax<'a>,
    pub(crate) source: &'a Source,
    pub(crate) print: Print,
    pub(crate) escaper: &'a str,
    pub(crate) ext: Option<&'a str>,
    pub(crate) mime_type: String,
    pub(crate) path: PathBuf,
}

impl TemplateInput<'_> {
    /// Extract the template metadata from the `DeriveInput` structure. This
    /// mostly recovers the data for the `TemplateInput` fields from the
    /// `template()` attribute list fields.
    pub(crate) fn new<'n>(
        ast: &'n syn::DeriveInput,
        config: &'n Config<'_>,
        args: &'n TemplateArgs,
    ) -> Result<TemplateInput<'n>, CompileError> {
        let TemplateArgs {
            source,
            print,
            escaping,
            ext,
            syntax,
            ..
        } = args;

        // Validate the `source` and `ext` value together, since they are
        // related. In case `source` was used instead of `path`, the value
        // of `ext` is merged into a synthetic `path` value here.
        let source = source
            .as_ref()
            .expect("template path or source not found in attributes");
        let path = match (&source, &ext) {
            (Source::Path(path), _) => config.find_template(path, None)?,
            (&Source::Source(_), Some(ext)) => PathBuf::from(format!("{}.{}", ast.ident, ext)),
            (&Source::Source(_), None) => {
                return Err("must include 'ext' attribute when using 'source' attribute".into())
            }
        };

        // Validate syntax
        let syntax = syntax.as_deref().map_or_else(
            || Ok(config.syntaxes.get(config.default_syntax).unwrap()),
            |s| {
                config
                    .syntaxes
                    .get(s)
                    .ok_or_else(|| CompileError::from(format!("attribute syntax {s} not exist")))
            },
        )?;

        // Match extension against defined output formats

        let escaping = escaping
            .as_deref()
            .unwrap_or_else(|| path.extension().map(|s| s.to_str().unwrap()).unwrap_or(""));

        let mut escaper = None;
        for (extensions, path) in &config.escapers {
            if extensions.contains(escaping) {
                escaper = Some(path);
                break;
            }
        }

        let escaper = escaper.ok_or_else(|| {
            CompileError::from(format!("no escaper defined for extension '{escaping}'"))
        })?;

        let mime_type =
            extension_to_mime_type(ext_default_to_path(ext.as_deref(), &path).unwrap_or("txt"))
                .to_string();

        Ok(TemplateInput {
            ast,
            config,
            syntax,
            source,
            print: *print,
            escaper,
            ext: ext.as_deref(),
            mime_type,
            path,
        })
    }

    pub(crate) fn find_used_templates(
        &self,
        map: &mut HashMap<PathBuf, Parsed>,
    ) -> Result<(), CompileError> {
        let source = match &self.source {
            Source::Source(s) => s.clone(),
            Source::Path(_) => get_template_source(&self.path)?,
        };

        let mut dependency_graph = Vec::new();
        let mut check = vec![(self.path.clone(), source)];
        while let Some((path, source)) = check.pop() {
            let parsed = Parsed::new(source, self.syntax)?;
            for n in parsed.nodes() {
                match n {
                    Node::Extends(extends) => {
                        let extends = self.config.find_template(extends.path, Some(&path))?;
                        let dependency_path = (path.clone(), extends.clone());
                        if dependency_graph.contains(&dependency_path) {
                            return Err(format!(
                                "cyclic dependency in graph {:#?}",
                                dependency_graph
                                    .iter()
                                    .map(|e| format!("{:#?} --> {:#?}", e.0, e.1))
                                    .collect::<Vec<String>>()
                            )
                            .into());
                        }
                        dependency_graph.push(dependency_path);
                        let source = get_template_source(&extends)?;
                        check.push((extends, source));
                    }
                    Node::Import(import) => {
                        let import = self.config.find_template(import.path, Some(&path))?;
                        let source = get_template_source(&import)?;
                        check.push((import, source));
                    }
                    _ => {}
                }
            }
            map.insert(path, parsed);
        }
        Ok(())
    }

    #[inline]
    pub(crate) fn extension(&self) -> Option<&str> {
        ext_default_to_path(self.ext, &self.path)
    }
}

#[derive(Debug, Default)]
pub(crate) struct TemplateArgs {
    pub(crate) source: Option<Source>,
    pub(crate) print: Print,
    pub(crate) escaping: Option<String>,
    pub(crate) ext: Option<String>,
    pub(crate) syntax: Option<String>,
    pub(crate) config: String,
    pub(crate) whitespace: Option<String>,
}

impl TemplateArgs {
    pub(crate) fn new(ast: &'_ syn::DeriveInput) -> Result<Self, CompileError> {
        // Check that an attribute called `template()` exists once and that it is
        // the proper type (list).
        let mut template_args = None;
        for attr in &ast.attrs {
            if !attr.path().is_ident("template") {
                continue;
            }

            match attr.parse_args_with(Punctuated::<syn::Meta, syn::Token![,]>::parse_terminated) {
                Ok(args) if template_args.is_none() => template_args = Some(args),
                Ok(_) => return Err("duplicated 'template' attribute".into()),
                Err(e) => return Err(format!("unable to parse template arguments: {e}").into()),
            };
        }

        let template_args =
            template_args.ok_or_else(|| CompileError::from("no attribute 'template' found"))?;

        let mut args = Self::default();
        // Loop over the meta attributes and find everything that we
        // understand. Return a CompileError if something is not right.
        // `source` contains an enum that can represent `path` or `source`.
        for item in template_args {
            let pair = match item {
                syn::Meta::NameValue(pair) => pair,
                _ => {
                    return Err(format!(
                        "unsupported attribute argument {:?}",
                        item.to_token_stream()
                    )
                    .into())
                }
            };

            let ident = match pair.path.get_ident() {
                Some(ident) => ident,
                None => unreachable!("not possible in syn::Meta::NameValue(…)"),
            };

            let value = match pair.value {
                syn::Expr::Lit(lit) => lit,
                syn::Expr::Group(group) => match *group.expr {
                    syn::Expr::Lit(lit) => lit,
                    _ => {
                        return Err(format!("unsupported argument value type for {ident:?}").into())
                    }
                },
                _ => return Err(format!("unsupported argument value type for {ident:?}").into()),
            };

            if ident == "path" {
                if let syn::Lit::Str(s) = value.lit {
                    if args.source.is_some() {
                        return Err("must specify 'source' or 'path', not both".into());
                    }
                    args.source = Some(Source::Path(s.value()));
                } else {
                    return Err("template path must be string literal".into());
                }
            } else if ident == "source" {
                if let syn::Lit::Str(s) = value.lit {
                    if args.source.is_some() {
                        return Err("must specify 'source' or 'path', not both".into());
                    }
                    args.source = Some(Source::Source(s.value()));
                } else {
                    return Err("template source must be string literal".into());
                }
            } else if ident == "print" {
                if let syn::Lit::Str(s) = value.lit {
                    args.print = s.value().parse()?;
                } else {
                    return Err("print value must be string literal".into());
                }
            } else if ident == "escape" {
                if let syn::Lit::Str(s) = value.lit {
                    args.escaping = Some(s.value());
                } else {
                    return Err("escape value must be string literal".into());
                }
            } else if ident == "ext" {
                if let syn::Lit::Str(s) = value.lit {
                    args.ext = Some(s.value());
                } else {
                    return Err("ext value must be string literal".into());
                }
            } else if ident == "syntax" {
                if let syn::Lit::Str(s) = value.lit {
                    args.syntax = Some(s.value())
                } else {
                    return Err("syntax value must be string literal".into());
                }
            } else if ident == "config" {
                if let syn::Lit::Str(s) = value.lit {
                    args.config = read_config_file(Some(&s.value()))?;
                } else {
                    return Err("config value must be string literal".into());
                }
            } else if ident == "whitespace" {
                if let syn::Lit::Str(s) = value.lit {
                    args.whitespace = Some(s.value())
                } else {
                    return Err("whitespace value must be string literal".into());
                }
            } else {
                return Err(format!("unsupported attribute key {ident:?} found").into());
            }
        }

        Ok(args)
    }
}

#[inline]
fn ext_default_to_path<'a>(ext: Option<&'a str>, path: &'a Path) -> Option<&'a str> {
    ext.or_else(|| extension(path))
}

fn extension(path: &Path) -> Option<&str> {
    let ext = path.extension().map(|s| s.to_str().unwrap())?;

    const JINJA_EXTENSIONS: [&str; 3] = ["j2", "jinja", "jinja2"];
    if JINJA_EXTENSIONS.contains(&ext) {
        Path::new(path.file_stem().unwrap())
            .extension()
            .map(|s| s.to_str().unwrap())
            .or(Some(ext))
    } else {
        Some(ext)
    }
}

#[derive(Debug)]
pub(crate) enum Source {
    Path(String),
    Source(String),
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub(crate) enum Print {
    All,
    Ast,
    Code,
    None,
}

impl FromStr for Print {
    type Err = CompileError;

    fn from_str(s: &str) -> Result<Print, Self::Err> {
        use self::Print::*;
        Ok(match s {
            "all" => All,
            "ast" => Ast,
            "code" => Code,
            "none" => None,
            v => return Err(format!("invalid value for print option: {v}",).into()),
        })
    }
}

impl Default for Print {
    fn default() -> Self {
        Self::None
    }
}

pub(crate) fn extension_to_mime_type(ext: &str) -> Mime {
    let basic_type = mime_guess::from_ext(ext).first_or_octet_stream();
    for (simple, utf_8) in &TEXT_TYPES {
        if &basic_type == simple {
            return utf_8.clone();
        }
    }
    basic_type
}

const TEXT_TYPES: [(Mime, Mime); 6] = [
    (mime::TEXT_PLAIN, mime::TEXT_PLAIN_UTF_8),
    (mime::TEXT_HTML, mime::TEXT_HTML_UTF_8),
    (mime::TEXT_CSS, mime::TEXT_CSS_UTF_8),
    (mime::TEXT_CSV, mime::TEXT_CSV_UTF_8),
    (
        mime::TEXT_TAB_SEPARATED_VALUES,
        mime::TEXT_TAB_SEPARATED_VALUES_UTF_8,
    ),
    (
        mime::APPLICATION_JAVASCRIPT,
        mime::APPLICATION_JAVASCRIPT_UTF_8,
    ),
];

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_ext() {
        assert_eq!(extension(Path::new("foo-bar.txt")), Some("txt"));
        assert_eq!(extension(Path::new("foo-bar.html")), Some("html"));
        assert_eq!(extension(Path::new("foo-bar.unknown")), Some("unknown"));

        assert_eq!(extension(Path::new("foo/bar/baz.txt")), Some("txt"));
        assert_eq!(extension(Path::new("foo/bar/baz.html")), Some("html"));
        assert_eq!(extension(Path::new("foo/bar/baz.unknown")), Some("unknown"));
    }

    #[test]
    fn test_double_ext() {
        assert_eq!(extension(Path::new("foo-bar.html.txt")), Some("txt"));
        assert_eq!(extension(Path::new("foo-bar.txt.html")), Some("html"));
        assert_eq!(extension(Path::new("foo-bar.txt.unknown")), Some("unknown"));

        assert_eq!(extension(Path::new("foo/bar/baz.html.txt")), Some("txt"));
        assert_eq!(extension(Path::new("foo/bar/baz.txt.html")), Some("html"));
        assert_eq!(
            extension(Path::new("foo/bar/baz.txt.unknown")),
            Some("unknown")
        );
    }

    #[test]
    fn test_skip_jinja_ext() {
        assert_eq!(extension(Path::new("foo-bar.html.j2")), Some("html"));
        assert_eq!(extension(Path::new("foo-bar.html.jinja")), Some("html"));
        assert_eq!(extension(Path::new("foo-bar.html.jinja2")), Some("html"));

        assert_eq!(extension(Path::new("foo/bar/baz.txt.j2")), Some("txt"));
        assert_eq!(extension(Path::new("foo/bar/baz.txt.jinja")), Some("txt"));
        assert_eq!(extension(Path::new("foo/bar/baz.txt.jinja2")), Some("txt"));
    }

    #[test]
    fn test_only_jinja_ext() {
        assert_eq!(extension(Path::new("foo-bar.j2")), Some("j2"));
        assert_eq!(extension(Path::new("foo-bar.jinja")), Some("jinja"));
        assert_eq!(extension(Path::new("foo-bar.jinja2")), Some("jinja2"));
    }
}